Lessons from Abroad

A typical Passivhaus design

Justin Bere of London-based Bere Architects believes that energy-saving German design methodology PassivHaus offers 'the best route to achieving the UK's zero-carbon housing goals'. This is a particularly pressing issue due to the government's aim for all new housing to be zero-carbon by 2016. Bere is working on his practice's first full PassivHaus, Smoothfield Farm near Ascot, Berkshire, scheduled to complete this year. It's one of a number of projects being developed under PassivHaus guidelines in the UK  as more and more architects and clients push to dramatically cut carbon emissions.

PassivHaus is based on enhancing building envelopes to reduce heating loads to the point that a conventional heating system can be eliminated. Developed from a German-Swedish academic collaboration in 1988, the first PassivHaus buildings were completed in 1991 in Darmstadt, Germany, the same city in which the PassivHaus Institute was founded five years later. Today, over 9,500 PassivHaus buildings have been realised in Germany, over 2,500 in Austria, and approximately 12,500 worldwide. Gavin Hodgson of the BRE estimates that the number of PassivHaus schemes in the UK is in the low hundreds. No exact figures are available because no UK building has attained PassivHaus designation yet, perhaps partly due to the £2,000 price tag for certification.

Eave which fails to meet the Passivhaus standard

This low take-up comes despite the BRE's commitment to PassivHaus – it participated in research shared between eight countries between 1998 and 2001, and developed a UK website (www.passivhaus.org.uk) and English translation of the PassivHaus computer modelling simulations (PHPP).

PassivHaus standards are roughly equivalent to Code for Sustainable Homes level four, two levels below the zero-carbon level six. The design heat load of a PassivHaus must be less than 15kWh/m2/year – which equals the heat that can be transported by the minimum required mechanical ventilation. Joints between materials and components and all service penetrations must be sealed.

Several UK practices are developing projects to PassivHaus standard. Youmeheshe director Simon Beames, whose firm looked to the method for its OKO House, says he first encountered PassivHaus through a competition win in 2006 which enabled him to tour several Austrian PassivHaus projects. 'I was amazed by the similarity between the internal air quality of the houses and the mountain air', he says.

Eave to Passivhaus standard

Beames notes that the biggest difference with the Austrian context is that while ground-source heating and solar panels can be relied upon to top up energy requirements in Austria's colder climate, the UK market must rely on biomass wood pellet boilers.

Construction quality and the high price of imported components are frequently mentioned barriers to the implementation of PassivHaus in the UK. Stephen Cartwright of Cardiff-based Passive Solutions, which distributes PassivHaus components such as triple-glazed windows and vacuum insulation, promotes UK manufacturing of these components. He adds: 'Training, such as the courses offered at [training centre] Pines Calyx in Kent, is critical to the achieving the necessary construction quality.'

Some architects remain sceptical of PassivHaus. Bill Dunster of ZEDFactory and Craig White of White Design are unsure if PassivHaus will work in the UK's mild climate, which makes mitigating electricity loads of mechanical ventilation harder to justify. White Design has developed the Bale House  to PassivHaus standard with maximum reliance on passive ventilation. 'There is a bit of a PassivHaus rush on in the UK,' White says. 'But we need to ask how it will really work here.'

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